1. Field of the Invention
Priority is claimed on Japanese Patent Application No. 2003-398917, filed Nov. 28, 2003, the contents of which are incorporated herein by reference.
The present invention relates to a fuel cell system having an anode gas supply device which supplies hydrogen to an anode electrode, and a cathode gas supply device which drives a compressor using electric power generated by the fuel cell, and supplies pressurized reaction gas to the cathode electrode. The present invention also relates to a control method for a fuel cell.
2. Description of Related Art
Recently, the development of fuel cell vehicles using electricity generated by a fuel cell is proceeding.
As this type of fuel cell vehicle, there is one where an anode gas supply device which supplies hydrogen to an anode electrode, and a compressor which supplies reaction gas to a cathode electrode are mounted within a vehicle, and hydrogen is supplied to the anode electrode and reaction gas to the cathode electrode to generate electricity. In practice, since electric power is required to drive the compressor, a part of the electric power generated by the fuel cell is consumed by the compressor. Moreover, since the electric power consumption of the compressor increases accompanying an increase in the electric power generated, it is not always efficient to increase the electric power generated to an unlimited extent. From this point of view, in Japanese Patent Application Unexamined Publication No. 8-45525, a technique is proposed to set the cathode pressure in accordance with the target generated current, so that the electric power generation efficiency of the fuel cell (overall efficiency in consideration of electric power consumption of the compressor) becomes a maximum.
However, the power generation efficiency of the fuel cell is insufficient if only the target generated current is considered, and it varies in accordance with environmental factors such as ambient temperature and pressure and the like. Therefore, there is the problem that in control with the aforementioned conventional technology, generation of electric power at sufficient efficiency is not possible in some cases.